Objective. To analyze the medical prescription, drug access and drug expenditure by patients based on the National Health Survey in Mexico, 1994. Materials and methods. A descriptive analysis of drug access and expenditure was undertaken and predictive factors for medical prescription were identified by logistic regression for 3 324 patients. Results. 78% of the patients received drug prescriptions. 92% of the Social Security patients and 35% of the Ministry of Health patients received drugs free of charge (p =0.000). The region with the highest poverty index received the least amount of drugs free of charge. Regarding drug expenditure of patients who purchased drugs, median expenditure was 40.00 pesos (12.50 USD). Private health service patients spent significantly more than public health service patients. Conclusions. Drug access and drug expenditure are linked to socioeconomic factors and to the institutions attended by patients. The Mexican health system faces, among others, the challenge of increasing the equity of access to medical drugs.